PRE~+: dual of proxy re-encryption for secure cloud data sharing service

摘要

>In this paper, aiming at providing secure cloud data sharing services in cloud storage, we propose a scalable and controllable cloud data sharing framework for cloud users: Scanf. Towards proposing this framework, we introduce a new cryptographic primitive: PRE+, which can be seen as the dual of traditional proxy re-encryption (PRE) primitive. All the traditional PRE schemes until now require the delegator (or the delegator and the delegatee cooperatively) to generate the re-encryption keys. We observe that the encrypter also has the ability to generate re-encryption keys. Based on this observation, we construct a new PRE+ scheme, which is almost the same as the traditional PRE except the re-encryption keys generated by the encrypter. Compared with PRE, PRE+ can easily achieve the non-transferable property and message-level-based fine-grained delegation. Our Scanf framework based on PRE+ can also achieve these two properties, which is very important for cloud storage sharing service.